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Maternal Age and Adverse Pregnancy Outcomes: A Cohort Study

Abstract

ABSTRACT: The association between maternal age 35 years or older and adverse pregnancy outcomes is increasingly important given the trend toward older maternal age at conception and childbirth in recent years. Adverse outcomes can include miscarriage, stillbirth, preeclampsia (PE), gestational hypertension (GH), gestational diabetes mellitus (GDM), preterm birth (PTB), delivery of a small (SGA) or large (LGA) for gestational age neonate, and elective or emergency cesarean section (CS). This retrospective study was designed to examine the association between maternal age and adverse pregnancy outcomes after adjustment for confounding factors in maternal characteristics and obstetric history.

At the first visit of the parturients, at 11 to 13 weeks’ gestation, maternal demographic characteristics and obstetric and medical histories were obtained by questionnaire and by standard physical examinations for the mother and sonographic evaluation of the fetus. Data on pregnancy outcomes were obtained from hospital maternity records and the parturients’ medical practitioners. Outcome measures included miscarriage, stillbirth, PE, GH, GDM, spontaneous and iatrogenic PTD at less than 34 weeks’ gestation, delivery of an SGA or LGA neonate, and delivery by elective or emergency CS. Maternal age (<35, 35–39.9, and ≥40 years) was considered a continuous and categorical variable with each complication. Odds ratios (ORs) with their confidence intervals (CIs) were calculated for the 2 older groups, with women younger than 35 years considered as a reference. Multivariable logistic regression analysis was performed for the prediction of each pregnancy outcome from maternal age and medical and obstetric history.

From 79,694 singleton pregnancies that were screened, the final cohort included 76,158 patients, with a median maternal age of 31.3 years (interquartile range, 26.8–35.2 years): 55,772 (73.2%) were younger than 35 years; 16,325 (21.4%) were 35 to 39 years; and 4061 (5.3%) were 40 years or older. Univariable logistic regression analysis showed that maternal age at 11 to 13 weeks was significantly associated with miscarriage, PE, GDM, delivery of an SGA or LGA neonate, and both elective and emergency CS, but not stillbirth, GH, or spontaneous PTD. On multiple logistic regression analysis, which adjusted for several maternal and pregnancy potential confounding variables, maternal age 40 years or older was associated with an increased risk of miscarriage (OR, 2.32; 95% CI, 1.83–2.93; P < 0.001), PE (OR, 1.49; 95% CI, 1.22–1.82; P < 0.001), GDM (OR, 1.88; 95% CI, 1.55–2.29; P < 0.001), SGA (OR, 1.46; 95% CI, 1.27–1.69; P < 0.001), and CS (OR, 1.95; 95% CI, 1.77–2.14; P < 0.001), but not with stillbirth, GH, spontaneous PTD, or LGA.

These outcomes confirm that older maternal age, after adjustment for other maternal characteristics and obstetric history, are associated with increased risk for several adverse outcomes. These findings should be of particular interest to the women and health care professionals because of the current trends in delayed childbearing secondary to improved access to education, career opportunities, and contraception and assisted reproductive techniques. Maternal age should be combined with other maternal characteristics and obstetric history when attempting to determine a woman’s individualized adjusted risk for adverse pregnancy complications.

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